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CFPS Research Archives

Follistatin

Early human Muscle & Bone Health 3 sources

Follistatin is a naturally occurring glycoprotein that binds to and neutralizes members of the TGF-β superfamily, most notably myostatin and activin. By inhibiting myostatin, a protein that restricts muscle growth, follistatin has been heavily researched for its potential to significantly increase muscle mass and strength, making it a target for treating muscle-wasting diseases.

01Dosing reference

Amount
100-300 mcg/day (highly variable in research)
Frequency
Daily or every other day for 10-30 days
Cycle
Short cycles of 2-4 weeks due to potential desensitization and off-target effects
Reference figures, not a recommendationThese values reflect amounts described in the literature and vendor documentation this database indexes. Use the reconstitution calculator to convert them into syringe units.

02Mechanism of action

01

Protein Binding

Follistatin binds directly to myostatin and activin A in the body.

02

Myostatin Inhibition

By neutralizing myostatin, it prevents myostatin from binding to its receptor (ActRIIB), thereby lifting the natural brake on muscle growth.

03

Muscle Hypertrophy

The removal of myostatin signaling leads to increased muscle cell size (hypertrophy) and potentially new muscle cell formation (hyperplasia).

03Human evidence

Gene therapy utilizing follistatin (AAV1-FS344) improved walking distance in patients with Becker muscular dystrophy.

Phase 1/2a clinical trial involving a small number of patients receiving intramuscular injections.

Follistatin gene therapy showed safety and potential efficacy in sporadic inclusion body myositis.

Early-stage human trial demonstrating improved muscle function and no severe adverse effects.

04Preclinical evidence

Significant increases in muscle mass and strength in mice.

Animal models with follistatin overexpression or administration showed dramatic muscle hypertrophy.

Improved muscle healing and reduced fibrosis after injury.

Rodent models of muscle injury treated with follistatin exhibited better regeneration.

05What is known vs. unknown

Reasonably established
  • Follistatin acts as a potent inhibitor of myostatin and activin.
  • It promotes significant muscle hypertrophy and strength gains in animal models.
  • Research is primarily focused on treating muscular dystrophies and muscle-wasting conditions.
  • Follistatin-344 (FS344) and Follistatin-315 (FS315) are common isoforms studied.
Unknowns & limits
  • Long-term safety and potential off-target effects of systemic follistatin administration in humans are largely unknown.
  • The optimal delivery method (e.g., gene therapy vs. recombinant protein injection) is still under investigation.
  • Potential impacts on reproductive hormones due to activin inhibition require further study.

06Safety & regulatory context

Regulatory statusFollistatin is an experimental compound and is not FDA-approved for human use outside of clinical trials. While early gene therapy trials for muscular dystrophy have shown a favorable safety profile, systemic administration of follistatin peptides carries unknown long-term risks. Because it inhibits activin, which plays a role in the reproductive system and other tissues, off-target effects are a concern. It is strictly for research purposes and is banned by the World Anti-Doping Agency (WADA) in sports.

07Compared with ACE-031

Follistatin vs. ACE-031
Key difference
Follistatin is a naturally occurring binding protein that neutralizes myostatin, whereas ACE-031 is a synthetic soluble receptor (ActRIIB-IgG1) designed to act as a decoy receptor for myostatin.
When researchers discuss each
Researchers discuss Follistatin when exploring natural regulatory pathways and gene therapy, while ACE-031 is discussed in the context of engineered decoy receptors for muscular dystrophy.

08Glossary

Myostatin
A protein produced and released by myocytes that acts on muscle cells' autocrine function to inhibit muscle growth.
Activin
A protein complex that enhances FSH biosynthesis and secretion, and participates in the regulation of the menstrual cycle and other biological functions.
Hypertrophy
The enlargement of an organ or tissue from the increase in size of its cells, commonly referring to muscle growth.

09Knowledge check

Q1What is the primary mechanism by which Follistatin promotes muscle growth?
Q2Which of the following is a potential concern with systemic Follistatin administration?
Q3Which limitation of the current human evidence for follistatin is directly indicated by the dossier?
Q4When researchers discuss follistatin rather than ACE-031, which research context is emphasized according to the dossier?
Q5Which statement best reflects the dossier's safety and regulatory context for follistatin?

10Sources

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GDF-8 Myostatin Inhibitor

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1 mg - 3 mg (highly variable depending on specific peptide/antibody)

ACE-031

Muscle & Bone Health
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ACE-031 is an investigational protein therapeutic designed to build muscle and increase strength by inhibiting signaling through the activin receptor type IIB (ActRIIB). Research primarily focused on its potential to treat muscle-wasting diseases like Duchenne muscular dystrophy, though clinical trials were halted due to safety concerns involving bleeding.

1-3 mg/kg (in clinical trial settings)
Research and educational use onlyNothing on this site is medical advice, a prescription, or a recommendation for human use. Compounds documented here are research chemicals. Consult a qualified clinician before making any health decision.